The use of airbag units is widespread in today's automotive technology. An airbag unit has at least one airbag enclosing at least one chamber and at least one inflator, in most cases in form of a gas generator for filling the chamber such that the airbag deploys.
Currently most airbag units are used for protecting an occupant (driver or passenger) sitting inside the passenger compartment of a motor vehicle. This means that the airbag of such an airbag unit deploys into the passenger compartment in order to restrain the occupant. Consequently the airbag of such an airbag unit must be relatively soft and the airbag usually has to include a ventilation opening for releasing inflation gas, such that kinetic energy can be dissipated.
Recently so called pedestrian airbags serving for the protection of a pedestrian involved in an accident have been introduced. Such pedestrian airbags usually cover at least a part of the windshield and/or a part of at least one A-pillar on the outside of the vehicle in order to prevent the pedestrian's head from hitting the windscreen or A-pillar. Such pedestrian airbags usually also need to be relatively soft in order to give the desired protection.
From EP 0 757 634 B1 it is known to place the airbag of an airbag unit between an element outside the passenger compartment and the passenger compartment in order to prevent that element from intruding into the passenger compartment in case of an accident. This element can for example be a wheel the engine block or another component. This measure can especially be useful for small and lightweight motor vehicles.
It is an object of the present invention to provide an improved airbag unit, especially for the use described in the generic EP 0 757 634 B1.
It is a further object of the invention to provide a motor vehicle with such an improved airbag unit.
An airbag that is used to prevent an element (for example a wheel) from intruding into a passenger compartment needs to possess several characteristics. First, it needs to be very sturdy, since high forces can be applied to it during the accident and because the airbag needs to be filled with a high pressure (for example 10 bars) in order to prevent the element from intruding into the passenger compartment. Typical airbags as described above are very likely to burst under such conditions. Second, such an airbag should not have a ventilation opening.
In order to comply with these requirements, the airbag of the airbag unit in accordance with this invention is made of a hose extending from a first end to a second end, wherein this hose is preferably in the form of a one-pieced woven hose element. This one-pieced woven hose element can be generally of the type as is used for fire hoses. Due to the one-piece woven structure such a hose element can withstand very high internal pressure forces.
Often, a relatively large thickness will be desired. In order to provide such a large thickness, it would in principle be possible to use a hose with a large diameter, but this would have several drawbacks. One of those is, that a doubling of the thickness (this means the doubling of the diameter of the hose) would lead to quadruplication of the volume to be filled by the inflator. So, according to the present invention, an airbag with two parallel sections is provided. These two sections are generated by folding the hose such that it is divided into the two sections with each section enclosing a chamber.
In order to retain the gas-tightness and robustness it is usually preferred to provide a separate gas feeding for each chamber. This makes it possible to fill both chambers through the ends (face-sides) of the hose, such that no additional holes in the lateral area of the hose that could weaken the airbag are necessary.
In order to get a simple, sturdy and compact design, it can further be preferred to provide a separate inflator for each chamber.
It is further preferred to provide a joint clamp for the two end areas of the hose. The two inflators or two tubes for filling the chambers can extend through the clamp, leading to a very compact design with a minimum of parts.
In order to improve the gas-tightness of the airbag, it can be preferred that the one-pieced-woven hose element is coated, especially on its inside. Silicone can be used for the coating.
As has already been mentioned, the airbag of the airbag unit according to the invention is especially useful for preventing an element of a motor vehicle which is located outside the passenger compartment from intruding into the passenger compartment during an accident. This element can especially be a wheel, and engine block, a battery, a part of the transmission of the vehicle or another component.
In the case that the element to be restrained is a wheel, the airbag will be located inside a wheel housing in most applications, but the invention can also be applied to motor vehicles that does not have a wheel housing, which can be the case especially with ultra-light electric cars.
Another application of the inventive airbag unit can be the use of the airbag as a seat lifter. Seat lifters can be used to help to restrain the pelvis of a passenger.